The objectives of this project have been to elaborate various aspects of the transport, absorption, excretion, and metabolism of phthalate esters in the rat. Metabolic fates of both the acid and alcohol moieties have been studied. The enzyme primarily responsible for hydrolysis of phthalate esters in vivo has been purified and characterized. A modified phthalate diester that is not metabolized in rats has been studied and found to have very low, if any, toxicity.